In two incidents 12 hours apart Friday at a John Brooks Food Store, 62 people complained of nausea, dizziness and weakness.

The cause of the first wave of illnesses involving 47 employees and customers was blamed on carbon monoxide fumes from a faulty propane-powered floor buffer. Gas levels were considered 40 times above what is considered lethal.

Ten were taken to the hospital Friday and all were released by that evening, said Kevin Henson, assistant chief for the Santa Fe Fire Department.

But what made the 15 employees sick Friday night remains a mystery.

Six of the 15 hospitalized were released Saturday and none were found to have any measurable level of carbon monoxide poisoning, Henson said.

"It's impossible that it was the same buffer," he said.

Authorities have closed down the food store and seven other businesses in the small shopping center in Edgewood, a rural community 30 miles east of Albuquerque.

Architects, the center's builder, air conditioning experts and others gathered for Saturday's investigation. A team in protective gear was examining the area for four possible toxins.

"We're one at a time going in and ruling out every possible source of toxic gas," Henson said. "As of yet, we've found nothing."

A decision was to be made early Saturday afternoon if the center would be allowed to reopen. Meanwhile, shop owners and others have been cooperative during the investigation. "They don't want people going back in the shops unless it is safe." Henson said.